1. Field of the Invention
The invention relates generally to the art of air-ride axle/suspension systems for heavy-duty wheeled vehicles, such as tractor-trailers or semi-trailers, which cushion the ride and stabilize the vehicle during operation. More particularly, the invention is directed to a height control valve assembly utilized in connection with air-ride axle/suspension systems. More specifically, the invention is directed to a height control valve and link that more efficiently connects the control arm of the height control valve to the beam of the air-ride axle/suspension system, eliminating the brackets and hardware typically associated with attaching the height control valve link to the frame of the vehicle and to the beam of the axle/suspension system. The height control valve assembly of the present invention results in fewer parts, reduced weight and more simplified installation of the height control valve and link, thereby reducing installation and maintenance cost, and reducing undesirable tolerance stacks associated with multiple bracket configurations prevalent in the prior art.
2. Background Art
Heavy-duty vehicles such as tractor-trailers typically include two or more leading or trailing arm suspension assemblies that connect the wheel bearing axles of the vehicle to the frame of the vehicle. Early suspension designs included heavy leaf-spring suspensions which resulted in a relatively rough ride to the cargo and/or passengers carried by the vehicle, and did not allow loads to equalize among the axles in all situations, thus creating the need for an axle/suspension system with softer ride characteristics and more efficient equalization characteristics. The subsequent development of air-ride axle/suspension systems provided greater load equalization among multiple axles for semi-trailers as well as improved ride quality for individual axles.
As a result, heavy-duty vehicles that transport freight often include leading or trailing arm air-ride axle/suspension systems, which use air springs to cushion the ride of the vehicle. Pneumatic control of these air springs is an important feature of air-ride axle/suspension systems. More particularly, it is important for a cushioned vehicle ride, and for optimum axle/suspension system performance and longevity to attempt to maintain a consistent predetermined distance between the vehicle frame and the travel surface. This predetermined distance is known in the art as the design ride height of the vehicle. The operating conditions of the vehicle must be considered in order to establish the design ride height of the vehicle. That is, when a heavy-duty vehicle executes certain maneuvers, such as making a hard turn or traveling over rough terrain, the forces imposed on the axle/suspension system by such maneuvers cause the axle/suspension system to articulate, or pivot and/or flex, beneath the vehicle frame which the system supports. Typically, an axle/suspension system is designed so that the anticipated range of articulation, pivoting and/or flexing occurs about a nominal predetermined position, and that nominal position is set as the design ride height of the vehicle. This articulation, pivoting and/or flexing can also be caused by the loading and unloading of the vehicle.
More specifically, after a heavy-duty vehicle is loaded with freight, or after freight is unloaded from the vehicle, the air springs of the axle/suspension system are adjusted to ensure that the vehicle is at design ride height. The adjustment of the air springs of the axle/suspension system is typically automatically accomplished by a height control valve assembly or leveling valve assembly which is in fluid communication with an air source and with the air springs. When the vehicle is loaded with freight and the air springs of the axle/suspension system are compressed, causing the vehicle frame to be positioned below design ride height or closer to the travel surface, compressed air is supplied to the air springs, thereby inflating/extending them and, in turn, causing the axle/suspension system to raise the vehicle frame to the design ride height. Conversely, when the vehicle is unloaded and the air springs of the axle/suspension system are extended, causing the vehicle frame to be positioned above design ride height or further away from the travel surface, air is exhausted from the air springs, thereby deflating/compressing them until the axle/suspension system lowers the vehicle frame to the design ride height.
To control the flow of air into the air springs, and the exhaustion of air from the air springs, a mechanically operated valve typically is employed, and is known in the art as a height control valve or leveling valve. The height control valve is typically mounted on a bracket that is in turn attached to the frame or hanger of the vehicle. The height control valve is in fluid communication with a compressed air source, such as an air supply tank, and is also in fluid communication with the vehicle air springs. The height control valve includes a control arm that is capable of being raised or lowered in order to direct air from the compressed air source to the air springs or alternatively from the air springs to atmosphere. The control arm is attached to a link that is bolted to the control arm on one end and bolted to a bracket at the other end. The bracket is in turn typically rigidly attached to the brake chamber mount of the brake assembly or to one of the beams of the axle/suspension system. The height control valve, along with the brackets and the link and the associated hardware that fastens these parts together, is known as the height control valve assembly. Adjustments to the height control valve assembly, including the link that controls activation of the valve, enable the design ride height to be achieved before the vehicle travels over the road.
Also, as the vehicle travels over the road and the driver executes maneuvers that cause the axle/suspension system to articulate between positions that compress the air springs and positions that extend them, the height control valve acts to maintain the design ride height. That is, when the air springs are compressed, the height control valve supplies air to the air springs from a vehicle air reservoir. Conversely, when the air springs are in an extended position, the height control valve exhausts air from the springs to atmosphere. The amount of air that is supplied or exhausted is based on the duration of the articulation and the flow rate of the height control valve at a given position.
Prior art height control valve assemblies often include links that are formed from metal plates having a plurality of aligned openings. The plates are attached to one another via fasteners that are disposed through selected ones of the aligned openings. By removing the fasteners and moving the plates in opposite directions with respect to one another and then replacing the fasteners, the length of the link can be increased or decreased. As a result, these types of prior art links are mechanically adjustable, which can potentially lead to improper adjustment of the ride height of the vehicle due to human error. Also, because prior art height control valve assemblies typically include brackets on the vehicle frame and brackets on the beam or brake chamber mount of the axle/suspension system that are distant from one another, the control arm of these prior art height control valve assemblies is quite long, resulting in a smaller range of activation, which can reduce performance of the height control valve. Moreover, because prior art height control valve assemblies include at least two brackets, one bracket attaching the height control valve to the vehicle frame or hanger, and the other bracket attaching the link of the height control valve to one of the beams or brake chamber mounts of the axle/suspension system, the combination of brackets and adjustable links make installation complicated, require increased maintenance and result in undesirable tolerance stacks that can potentially cause an inaccurate design ride height for the vehicle.
The height control valve assembly of the present invention solves the problems associated with prior art height control valve assemblies by utilizing a height control valve that mounts directly to the vehicle frame and which incorporates a non-adjustable wire link that attaches directly to one of the beams of the axle/suspension system, thereby eliminating all of the brackets and associated hardware of the prior art height control valve assemblies, resulting in easier installation, decreased maintenance costs and reduced weight. Moreover, because the brackets attaching the height control valve assembly to the frame or hanger and the beam are eliminated, the height control valve assembly of the present invention reduces undesirable tolerance stacks associated with those brackets, and thereby reduces the possibility of human error adversely affecting the design ride height of the vehicle. The height control valve assembly of the present invention also allows for utilization of a relatively shorter control arm, that in turn allows a wider range of activation for the height control valve, resulting in increased sensitivity and performance of the system.